How to use this image

This can be used in the same way as Official Ruby Image. Please see "How to use this image" section of it with replacing the image name with this one.

How to install C extension etc.

This doesn't contain a compiler, a linker and headers etc. so if you'd like to add a something C extension for Ruby, first you need to install them by tce-load command. Please refer this image's Dockerfile which is a good example of installing those packages.